To diagnose disease in the breast tissue of women, dedicated local coil systems that may include a plurality of individual coils are used in magnetic resonance imaging to improve image quality (e.g., signal-to-noise ratio or SNR). For a magnetic resonance imaging examination of a breast, the patient is positioned in a prone position, such that one or both breasts may hang in cutouts in the local coil system. An optimized antenna array having a plurality of individual coils that act as MR reception antennas is placed around the openings in the interior of the housing of the local coil system. The individual coils are connected to the MRI system via active low-noise preamplifiers (LNAs).
To maximize the number of patients that may be examined using the local coil system, the cutouts in the local coil system may be configured to accommodate the maximum expected breast volume to be examined. However, the dimensions of the female breast vary greatly. As a result, although the local coil system has a high fill factor for patients with a large breast volume, the local coil system has a poor fill factor for patients with a small breast volume. Since the fill factor and, therefore, the distance of the tissue from the individual coils of the local coil system exert a direct influence on the achievable SNR, a loss in image quality may result for patients with a small breast volume.
The document DE 44 34 949 C2 describes an antenna arrangement of a local coil system for the magnetic resonance (MR) examination of a female breast. The problem of adaptation to different breast sizes is neither mentioned nor solved.
The document DE 10 2005 024 325 A1 describes a local coil system that is adapted for the MR examination of a female breast. The local coil system is in the form of a vest-shaped carrier part that the patient wears during examination. The vest-shaped carrier part may adapt itself to the female anatomy. With respect to the problem of adaptation to varying breast sizes, document DE 10 2005 024 325 A1 mentions only that breast tissue may be stabilized by insertion of a vacuum cushion. However, there is no description of adapting the antenna geometry to a smaller breast.
The document DE 10 2007 047 020 B4 describes an MRI system with an arrangement for transmitting magnetic resonance signals. The arrangement includes a local coil system for receiving radiofrequency signals from a magnetic resonance examination using a number of individual coils. The arrangement further includes passive individual antennae that are electromagnetically coupled to the individual coils of the local coil. The individual coils of the local coil system and the passive individual antennae are coupled to one another. Although the antenna arrangement described in document DE 10 2007 047 020 B4 presents a physical principle underlying improved SNR, the document does not describe any use of the principle within the field of mammographic MRI examinations. Moreover, the document does not describe the use of the principle with cushions for fixating the breast. Furthermore, the document does not describe any materials with a high permittivity.